The present invention relates to a method for casting a cast part onto the end of a hollow section,and, more particularly, to a casting method in which the end of the hollow section is placed in a defined position in a die, the die is closed, the end opening in the hollow section is closed in a sealed manner against the penetration of cast material, at least during casting, the molten cast material is introduced into the remaining free space in the die and the hollow section is thereby cast around in a positive-locking manner, at least at the end.
German Auslegeschrift 2,725,979 describes production of a bicycle frame from tubes, with the tube ends being connected to one another in the region of a frame intersection by a pressure die-cast part cast on in a positive-locking manner. To prevent the open ends of the tubes from being filled with the molten material of the pressure die-cast part during the casting of the said pressure die-cast part, these openings are closed by caps. Protection against the tubes being pulled out of the cast part after it has cooled is achieved by providing the cast-around end sections of the tubes with notches, holes, undercuts and/or expanded portions or the like, behind or around which the cast material flows during the casting of the cast part. Despite the positive engagement between the tube and the cast part, this joint is sensitive to severe vibration such as that which acts, for example, on a motor vehicle door.
German Patent 521,654 describes tubes cast-around in a positive-locking manner at the ends by a pressure die-cast part. To increase the strength of the joint, the tubes are expanded in a dovetail shape in their cast-around end section. To cast on the pressure die-cast part, the openings in the ends of the tubes are temporarily closed by a casting core. To ensure that there is fluid communication between the tubes and the hollow cast part, the casting core is removed after the solidification of the pressure die-cast part. However, casting with a casting core is expensive since it is first necessary to produce the casting core and then remove it again. Moreover, this joint between the tube and cast part is also sensitive to severe vibration.
It is an object of the present invention to develop a method for casting a cast part onto the end of a hollow section in which the joint between the cast part and the hollow section is insensitive to vibrations.
The foregoing object has been achieved according to the present invention by a method in which the hollow section is cooled during the casting of the cast part, in that the material at the end of the hollow section to be embedded is deformed by the cast material during casting and in that the deformed material of the hollow section is pressed into positive engagement with a groove on the closure. By virtue of the cooling of the hollow section during casting, the cast material approaches more closely the dimensions which the hollow section has at normal temperature since the hollow section is subject to less thermal expansion than in the conventional methods. Because the cast material then shrinks to a greater extent relative to the hollow section, when the cast part cools, the hollow section is then compressed more strongly in the cast part than hitherto. This stronger compression increases the strength of the joint between the cast part and the hollow section.